The present invention relates to a printed wiring board and its manufacturing method, and particularly relates to a printed wiring board capable of forming a very small opening portion and a hole for conductivity and be mounted at high density, an electric conducting method between upper and lower faces of an insulating substrate, electric connection of a pad for external connection and the hole for conductivity, and a plating lead used in electric plating.
As shown in FIGS. 28 and 29, conventionally there is a printed wiring board having a mounting portion 970 for mounting electronic parts to an insulating substrate 97 and a conductor circuit 96 arranged around this mounting portion 970. A bonding pad portion 969 forming an end tip of the conductor circuit 96 is formed near the mounting portion 970. A pad portion 961 for joining a soldering ball, etc. is formed in the conductor circuit 96.
The mounting portion 970 is constructed by a concave portion surrounded by a mounting hole 971 formed in the insulating substrate 97 and a heat radiating plate 98 covering one end of the mounting hole 971.
As shown in FIG. 29, a surface of the insulating substrate 97 is covered with an insulating film 91 except for the pad portion 961 and the bonding pad portion 969. In other words, this insulating film 91 exposes the pad portion 961 and the bonding pad portion 969 by arranging an opening portion 910 above the pad portion 961 and the bonding pad portion 969.
A manufacturing method of the above printed wiring board will be explained next.
First, as shown in FIG. 30, a mounting hole 971 is bored in an insulating substrate 97 which is sticking a copper foil thereto. Next, the copper foil is etched so that a conductor circuit 96 having a pad portion 961 and a bonding pad portion 969 is formed.
Next, as shown in FIG. 28, solder resist constructed by thermosetting resin is printed on a surface of the insulating substrate 97. At this time, surfaces of the above pad portion 961 and the bonding pad portion 962 are exposed as they are without the solder resist printing.
Next, the solder resist is thermally cured and is set to an insulating film 91.
Thereafter, a heat radiating plate 98 is adhered to the surface of the insulating substrate 97 by using an adhesive 981 so as to cover one end of the mounting hole 971.
Thus, a printed wiring board 9 is obtained.
However, the above conventional manufacturing method of the printed wiring board 9 has the following problems.
Specifically, as shown in FIG. 31, except for a portion of the pad portion 961 no very small opening portion 910 can be formed in the insulating film 91 in a method for partially printing the above solder resist. Therefore, it is impossible only to expose a very small portion in the conductor circuit 96. As a result, no high density mounting can be improved.
In contrast to this, a manufacturing method as shown in FIG. 32 is proposed. In this method, an entire surface of the insulating substrate 97 forming the conductor circuit 96 therein is covered with a solder resist 912 constructed by an optical curing type resin. The solder resist 912 is exposed in a state in which a light interrupting mask 94 is arranged above an opening portion forming portion.
In this method, the solder resist 912 in a portion of light 940 interrupted by the mask 94 is not cured and is left as it is. In this state, the solder resist in an exposed portion is cured and forms an insulating film. Next, the insulating substrate 97 is dipped into a developing liquid and the solder resist in an uncured portion is removed from the insulating substrate 97. Thus, an opening portion 910 is formed in the cured insulating film 91 and one portion of the conductor circuit 96 is exposed.
However, in this method, since the optical curing type resin used as the solder resist has a property of absorbing humidity, no solder resist is suitable as the insulating film.
Further, since the above light has scattering light, the above light cannot be sufficiently interrupted so that no opening portion 910 can be formed in a sharp state. Therefore, for example, it is almost impossible to form a very small opening portion having a size equal to or smaller than 0.60 mm. Therefore, no high density mounting can be improved.
By using a drill there is also the method for boring a hole for conductivity. However, in this case, it is also difficult to form a very small hole for conductivity.
Further, there is a case in which various kinds of conductive members are formed around the hole for conductivity. Tangibly, such conductive members are constructed by a land surrounding a peripheral portion of the hole for conductivity, a pad for externally joining a soldering ball, a plating lead for forming electric plating, etc. High density is also desirable when these conductive members are formed.
With consideration to such conventional problems, the present invention provides a printed wiring board able to form an insulating film having a very small opening portion and be mounted at high density, and a manufacturing method of the printed wiring board.
A first invention is a manufacturing method of a printed wiring board characterized in that a conductor circuit is formed on the surface of an insulating substrate;
a solder resist made of thermosetting resin is next printed on the surface of said insulating substrate;
an insulating film having a coefficient thermal expansion equal to or smaller than 100 ppm/xc2x0C. is next formed by thermally curing the solder resist; and
the conductor circuit is next exposed by irradiating a laser beam to an opening portion forming portion in the insulating film and burning-out the insulating film of said opening portion forming portion and forming an opening portion.
An operation and effects of the first invention will be explained.
In the first invention, the entire surface of the insulating substrate is covered with the insulating film and the laser beam is irradiated to a portion for forming the opening portion. High energy is given by a laser to the irradiating portion of the laser beam so that this irradiating portion has a very high temperature and is burnt out. Therefore, a very small opening portion can be formed in the insulating film.
Further, no light is scattered since the laser beam is parallel light. Therefore, a very small opening portion having an approximately size from 0.05 to 0.60 mm can be formed in desirable position and size. Accordingly, many opening portions can be formed in a small space so that high density mounting can be realized.
Thermosetting resin used in the solder resist has a low coefficient thermal expansion equal to or smaller than 100 ppm/xc2x0C. Therefore, the thermosetting resin has a property in which generation of stress of the solder resist is reduced by a temperature cycle test, etc. Accordingly, a close attaching property of the solder resist and the conductor circuit is improved.
In contrast to this, when the coefficient thermal expansion exceeds 100 ppm/xc2x0C., a problem exists in that the stress of the solder resist is increased by the temperature cycle test, etc.
A lower limit of the coefficient thermal expansion of the thermosetting resin includes 0 ppm/xc2x0C., but is preferably set to 1 ppm/xc2x0C. to more effectively show the above effects of the present invention.
The coefficient thermal expansion of the thermosetting resin used in the solder resist is preferably further set to range from 30 to 50 ppm/xc2x0C.
The above solder resist is preferably constructed by epoxy resin, triazine resin, polyimide resin, or a modified material thereof. In this case, a heat resisting close attaching property is improved between the solder resist and the conductor circuit. Further, an insulating substrate having a low water absorbing ratio is obtained through thermal curing of the solder resist.
A metallic plating film is preferably formed on a surface of the exposed conductor circuit after the laser beam is irradiated to the opening portion forming portion in the above insulating film. In this case, a solder leaking property on the conductor circuit surface is improved. Further, corrosion of the conductor circuit can be prevented.
Desmear processing is preferably performed on the surface of the exposed conductor circuit after the irradiation of said laser beam. The desmear processing is the processing for dissolving and removing the residue of the solder resist left on the surface of the exposed conductor circuit by a drug. In this case, the surface of the exposed conductor circuit is washed so that adhesive strength of the metallic plating film is improved. For example, the drug for the desmear processing is constructed by concentrated sulfuric acid, chromic acid, both of these mixed acid, or an acid obtained by adding sodium permanganate and potassium permanganate to each of these acids.
When the desmear processing is performed, there is a case in which the insulating film is separated from the insulating substrate on an interface with this insulating substrate at a peripheral edge of the opening portion in accordance with a kind of the solder resist forming the insulating film. Therefore, when the desmear processing is performed, the above solder resist is preferably constructed by thermosetting resin. The thermosetting resin has a resisting property with respect to a strong acid used in the desmear processing. Therefore, the separation of the insulating film at the peripheral edge of the opening portion can be prevented by using the thermosetting resin as the solder resist. For example, this thermosetting resin is constructed by epoxy resin, polyimide resin, triazine resin, etc.
A second invention is a printed wiring board characterized in that an upper face pattern is formed on an upper face of an insulating substrate and a lower face pattern is formed on a lower face of said insulating substrate and a hole for conductivity extends through said insulating substrate and reaches an upper face of said lower face pattern, and a metallic filling material filled with a metal for electrically conducting said upper face pattern and said lower face pattern is arranged within the hole for conductivity; and said upper face pattern has a width from 0.05 to 0.2 mm around said hole for conductivity.
In the second invention, it is most noticeable that the metallic filling material for electrically conducting the upper face pattern and the lower face pattern is arranged within the hole for conductivity.
An operation and effects of the second invention will be explained.
The hole for conductivity extends through the insulating substrate and a lower end portion of the hole for conductivity is closed by the lower face pattern. In contrast to this, the upper face pattern is arranged around an upper end portion of the hole for conductivity. Therefore, the upper face pattern and the lower face pattern can be electrically conducted to each other through the metallic filling material by forming the metallic filling material within the hole for conductivity.
The metallic filling material within the hole for conductivity is joined to the upper face pattern at least on a side face of an upper end portion of the metallic filling material. Therefore, the upper face pattern can be joined to the metallic filling material irrespective of the large or small value of a width of the upper face pattern, and the upper face pattern and the hole for conductivity can be electrically conducted reliably.
Therefore, it is not necessary that the width of a plating attaching area for forming a plating film in the hole for conductivity is formed in the upper face pattern as in the conventional case. Consequently, in accordance with the present invention, the width of the upper face pattern arranged around the hole for conductivity can be reduced to a width of 0.05 to 0.2 mm. Further, a surplus area is formed on a surface of the insulating substrate by the reduction in the width of the upper face pattern. Accordingly, another upper face pattern, an electronic part mounting portion, etc. can be further formed in this surplus area so that high density mounting can be achieved.
The second invention can also be applied to a multilayer printed wiring board having two or more insulating substrates laminated to each other as well as the printed wiring board constructed by a single insulating substrate. In the case of the multilayer printed wiring board, the hole for conductivity for electrically conducting the upper face pattern and the lower face pattern can be arranged such that this hole for conductivity extends through each insulating substrate. Further, this hole for conductivity can also be arranged such that this hole continuously extends through plural insulating substrates. In the multilayer printed wiring board, there is a case in which the upper face pattern or the lower face pattern is set to an inner layer pattern and is also set to an outer layer pattern.
The above metallic filling material is preferably constructed by solder. In this case, the interior of the hole for conductivity is easily filled with the solder since the solder is melted at a low temperature. Further, the joining can be performed at low cost since the soldering material is cheap.
The above metallic filling material is preferably constructed by a plating deposit material in which a plating layer is deposited on the above lower face pattern within the above hole for conductivity. In the plating deposit material, the metallic filling material is formed within the hole for conductivity by sequentially depositing a metal from an upper face of the lower face pattern within the hole for conductivity and/or a wall face of the hole for conductivity. Thus, the metallic filling material can be easily formed within the hole for conductivity.
In particular, the plating deposit material is preferably formed by using an electric plating method. This is because the metallic filling material can be rapidly formed since the depositing speed of a metal in the electric plating method is higher than that in a chemical plating method. In particular, the electric plating method is preferably used when the insulating substrate is thin in thickness and the hole for conductivity is shallow in depth. This is because the metallic filling material can be rapidly formed since a depositing thickness from the upper face of the lower face pattern may be set to be thin.
The above upper face pattern is preferably covered with a resist film except for a peripheral portion of the above hole for conductivity. In this case, the interior of the hole for conductivity can be filled with the metal without attaching the metal for forming the metallic filling material to the upper face pattern near the peripheral portion of the hole for conductivity.
As a method for manufacturing the printed wiring board as the second invention, there is a manufacturing method of a printed wiring board characterized by an upper face pattern formed on an upper face of an insulating substrate around a forming portion of a hole for conductivity so as to surround this forming portion of the hole for conductivity, and a lower face pattern is formed on a lower face of said insulating substrate so as to cover said forming portion of the hole for conductivity; the hole for conductivity extending through said insulating substrate and reaching an upper face of said lower face pattern is next formed in the forming portion of the hole for conductivity in said insulating substrate; and a metallic filling material is next formed by filling the interior of said hole for conductivity with a metal so that said upper face pattern and said lower face pattern are electrically conducted to each other through the metallic filling material.
In this manufacturing method, after the upper face pattern and the lower face pattern are formed in the insulating substrate, the metallic filling material is formed within the hole for conductivity in a state in which the hole for conductivity is set to a non-through hole by covering a lower end of the hole for conductivity with the lower face pattern. Therefore, the upper face pattern and the lower face pattern can be conducted to each other electrically through the metallic filling material.
Further, since the electric conduction is performed by the metallic filling material formed within the hole for conductivity, it is not necessary that the width of a plating attaching area for forming a plating film in the hole for conductivity is formed in the upper face pattern. Accordingly, the width of the upper face pattern arranged around the hole for conductivity can be reduced in comparison with the conventional case. Therefore, an upper face pattern, an electronic part mounting portion, etc. can be formed by the reduction in the width of the upper face pattern so that high density mounting can be achieved.
When the above hole for conductivity is formed, a laser beam is preferably irradiated to the forming portion of the hole for conductivity in the insulating substrate. In this case, the hole for conductivity as a non-through hole can be easily formed in the forming portion of the hole for conductivity.
In particular, the hole for conductivity having a small diameter can be accurately formed since the laser beam can bore the hole locally.
Before the interior of the above hole for conductivity is filled with the metal, the upper face of the above insulating substrate is preferably covered with a resist film except for the above hole for conductivity. In this case, when the interior of the hole for conductivity is filled with the metal, no upper face pattern is stained by attaching the metal to this upper race pattern, etc.
The metal filling the interior of the above hole for conductivity is constructed preferably by solder. It is also preferable to fill the interior of the above hole with the metal by depositing a plating layer on the upper face of the above lower face pattern within the above hole for conductivity. In these cases, as mentioned above, the interior of the hole for conductivity can be easily filled with the metal.
The second invention can be utilized in a multilayer printed wiring board requiring high connection reliability such as a memory module, a multichip module, a mother board, a daughter board, a plastic package, etc.
A third invention is a printed wiring board having an insulating substrate constructed by one, two or more insulating layers, a pad for external connection arranged in an outermost layer of the insulating substrate, a conductor pattern arranged in another layer different from said outermost layer, and a hole for conductivity for electrically connecting said pad for external connection and said conductor pattern; the printed wiring board characterized with said pad for external connection closing an opening portion of the hole for conductivity on its outermost layer side forming a bottom portion of the hole for conductivity, and a metallic plating film for continuously covering an inner wall and the bottom portion of the hole for conductivity is formed within said hole for conductivity.
An operation and effects of the third invention will be explained.
The pad for external connection is arranged so as to form the bottom portion of the hole for conductivity. Therefore, it is not necessary to form a conductor pattern for connecting the hole for conductivity and the pad for external connection. Accordingly, a surplus area is formed on a surface of the insulating substrate and another conductor pattern, etc. can be further formed in this surplus area so that high density surface mounting can be obtained. Further, the distance between respective holes for conductivity can be reduced so that the holes for conductivity can be formed at high density.
The pad for external connection closes the opening portion of the hole for conductivity on its outermost layer side and forms the bottom portion of the hole for conductivity. Therefore, the pad for external connection has at least one area of the opening portion of the hole for conductivity. Hence, the pad for external connection can secure a sufficient joining area for joining an external connecting terminal and has an excellent joining strength to the external connecting terminal.
The metallic plating film for continuously covering the inner wall and the bottom portion of the hole for conductivity is arranged within the hole for conductivity. Therefore, the bottom portion of the pad for external connection is strongly joined to the metallic plating film so that joining strength to the hole for conductivity is improved. Hence, for conductivity the pad for external connection can be reduced to a size close to that of the opening portion of the hole.
Accordingly, it is possible to realize high density mounting of the pad for external connection and increase density of surface mounting of the insulating substrate.
For example, the above conductor pattern is all conductive patterns which are able to be formed on the surface of the insulating substrate such as a wiring circuit, a pad, a terminal, a land, etc. For example, the conductor pattern is formed from etching of a metallic foil, metallic plating, etc.
The above insulating layer is constructed from a synthetic resin simple substance, a resin basic material constructed by synthetic resin and an inorganic filler, a cloth basic material constructed by synthetic resin and an inorganic cloth, a prepreg, etc. The above synthetic resin is constructed by epoxy resin, phenol resin, polyimide resin, polybutadiene resin, fluoride resin, etc.
The third invention can be utilized in a multilayer printed wiring board requiring high connection reliability such as a memory module, a multichip module, a mother board, a daughter board, a plastic package, etc.
An external connecting terminal is preferably joined to a surface of the above pad for external connection in a central position of the hole for conductivity. In this case, the external connecting terminal can be stably joined to the surface of the pad for external connection.
The above external connecting terminal is preferably constructed by a soldering ball, a probe, conductive paste or a conductive wire. This is because these external connecting terminals can exactly input and output electric information transmitted to the pad for external connection.
When the printed wiringboard of the above third invention is manufactured, there is a manufacturing method of a printed wiring board in which a conductor pattern is formed on an upper face of an insulating layer and a pad for external connection is formed on a lower face of the insulating layer, and said conductor pattern and the pad for external connection are electrically connected to each other by a hole for conductivity; the manufacturing method being characterized by an upper face copper foil and a lower face copper foil which are first respectively stuck to the upper and lower faces of the insulating layer; an opening hole is next formed by removing a portion corresponding to a forming portion of the hole for conductivity in said upper face copper foil by etching; the hole for conductivity is next formed in the insulating layer exposed from the opening hole of said upper face copper foil, and a bottom portion of the hole for conductivity is set to reach said lower face copper foil; a chemical plating film is next formed in an inner wall of the hole for conductivity; an electric plating film for continuously covering the inner wall and the bottom portion of the hole for conductivity is next formed within the hole for conductivity; a conductor pattern electrically connected to said hole for conductivity is next formed from the upper face copper foil from etching said upper face copper foil and the lower face copper foil, and a pad for external connection for closing an opening portion of said hole for conductivity is formed from said lower face copper foil.
In this manufacturing method, it is most noticeable that the pad for external connection is formed from etching the lower face copper foil constituting the bottom portion of the hole for conductivity after the hole for conductivity is formed and the inner wall and the bottom portion of the hole for conductivity are covered with the metallic plating film.
After the bottom portion of the hole for conductivity is formed in order to reach the lower face copper foil, the electric plating film for continuously covering the inner wall and the bottom portion of the hole for conductivity is formed in the hole for conductivity. The electric plating film is closely attached to the lower face copper foil as the bottom portion of the hole for conductivity. Therefore, the pad for external connection can be securely closely attached to the electric plating film within the hole for conductivity even when the pad for external connection is reduced to a size approximately similar to that of the hole for conductivity from etching the lower face copper foil.
Therefore, a surplus area is formed on the lower face of the insulating layer by reducing the size of the pad for external connection. Another pad for external connection, a conductive layer, etc. can be further mounted to this surplus area at high density.
For example, there is a method for irradiating a laser beam to the forming portion of the hole for conductivity in the insulating layer as a method for forming the hole for conductivity in the above insulating layer.
The laser beam sequentially bores a hole within the insulating layer by giving high energy to the insulating layer. The laser beam is reflected on the lower face copper foil when an end tip of the laser beam reaches the lower face copper foil. Therefore, when the irradiation of the laser beam is stopped here, a non-through hole for conductivity having one opening portion covered with the lower face copper foil is formed.
It is noticeable here that the non-through hole reaching the lower face copper foil can be formed by irradiating the laser beam. Conventionally it is necessary that a hole is bored in the insulating layer by a drill and a router and an opening portion of this hole is then covered with a copper foil to form such a non-through hole. However, the non-through hole reaching the lower face copper foil can be formed by irradiating the laser beam so that no covering work of the opening portion is required after the boring. Therefore, the number of manufacturing processes is reduced and manufacturing cost can be reduced.
The conductor pattern formed on the upper surface of the insulating layer, and the pad for external connection formed on the lower face of the insulating layer can be simultaneously formed by etching the upper face copper foil and the lower face copper foil. Accordingly, the printed wiring board can be manufactured efficiently and easily.
After the above conductor pattern and the pad for external connection are formed, one, two or more other insulating layers are preferably laminated with the above insulating layer having the pad for external connection in a state in which the above pad for external connection is arranged in an outermost layer. In this case, high density mounting of the printed wiring board can be obtained.
An external connecting terminal is preferably joined to a surface of the above pad for external connection in a central position of the hole for conductivity. In this case, similar to the above-mentioned invention of claim 2, the external connecting terminal can be joined to the pad for external connection in a stable state.
A fourth invention is a manufacturing method of a printed wiring board having a conductor pattern covered with an electric plating film on the surface of an insulating substrate; the manufacturing method being characterized in that the manufacturing method comprises a process for forming the conductor pattern on the surface of the insulating substrate and forming a plating lead electrically connected to the conductor pattern; a process for covering a surface of the conductor pattern with the electric plating film by flowing an electric current to the conductor pattern through said plating lead; and a process for melting and cutting the plating lead by irradiating a laser beam to said plating lead.
In the fourth invention, it is most noticeable that the plating lead is melted and cut by the laser beam after the electric plating film is formed on the surface of the conductor pattern by using the plating lead.
An operation and effects of the fourth invention will be explained.
Coherent light having aligned phases is obtained by the laser beam so that directivity is good. Therefore, high energy can be given to a very small portion by irradiating the laser beam. Hence, only the plating lead can be melted and cut without damaging the conductor pattern arranged around the plating lead even when the plating lead is finely constructed. Accordingly, the plating lead can be formed in a very small pattern so that the distance between conductor patterns can be reduced to 0.3 mm at its minimum. Accordingly, high density mounting of the conductor patterns can be realized in accordance with the present invention.
The above laser beam is preferably constructed by using an excimer laser, a carbon dioxide gas laser, etc.
The laser beam preferably has energy intensity set such that the plating lead is sufficiently melted and cut and no insulating substrate below the plating lead is damaged. For example, such energy intensity is set such that a wavelength ranges from 20 nm to 10 xcexcm and an output ranges from 30 to 300 W and an irradiating time ranges from 0.1 to 1.0 second.
A melting and cutting state of the plating lead using the laser beam is adjusted by the energy intensity of the laser beam, the irradiating time, etc.
The above electric plating film can be formed by a general electric plating method. For example, the electric plating film can be formed by depositing a metal on the surface of the conductor pattern by flowing an electric current to the conductor pattern through the plating lead in a state in which the insulating substrate is dipped into an electric plating reservoir.
For example, the above conductor pattern is all conductive patterns able to be formed on the surface of the insulating substrate such as a wiring circuit, a pad, a terminal, a land, etc. For example, the conductor pattern is formed by etching of a metallic foil, metallic plating, etc.
The above insulating substrate is constructed by a synthetic resin simple substance, a resin basic material constructed by synthetic resin and an inorganic filler, a cloth basic material constructed by synthetic resin and an inorganic cloth, etc. The above synthetic resin is constructed by epoxy resin, phenol resin, polyimide resin, polybutadiene resin, fluoride resin, etc. These insulating substrates can be laminated with other insulating substrates by interposing an adhesive such as a prepreg, etc. so that a multilayer printed wiring board can be constructed.
There is a manufacturing method of the printed wiring board for forming the electric plating film in an inner wall of the through hole in addition to the surface of the conductor pattern by utilizing the above fourth invention. This manufacturing method is a manufacturing method of a printed wiring board in which the printed wiring board has a conductor pattern formed on the surface of an insulating substrate and also has a through hole extending through said insulating substrate, and a surface of said conductor pattern and an inner wall of the through hole are covered with an electric plating film; the manufacturing method being characterized in that the manufacturing method comprises a process for boring the through hole in the insulating substrate; a process for forming a chemical plating film in the inner wall of said through hole; a process for forming the conductor pattern on the surface of said insulating substrate, and forming a plating lead for electrically connecting the conductor pattern and said chemical plating film within the through hole; a process for covering surfaces of the conductor pattern and said chemical plating film with the electric plating film by flowing an electric current to the conductor pattern and said chemical plating film through said plating lead; and a process for melting and cutting the plating lead by irradiating a laser beam to said plating lead.
When the electric plating film is formed in the inner wall of the through hole, the chemical plating film is formed by the chemical plating method in this inner wall after the through hole is bored. Thus, conductivity is given to the inner wall of the through hole. An electric current is flowed to the chemical plating film covering the inner wall of the through hole through the plating lead in a state in which the insulating substrate is dipped into an electric plating reservoir. Thus, a metal is deposited on the surface of the chemical plating film so that the electric plating film is formed.
Similar to the above fourth invention, the plating lead connected to the through hole and the conductor pattern is also melted and cut by irradiating the laser beam in this manufacturing method after the electric plating film is formed. Therefore, the plating lead can be set to a very small portion so that both of distances between through holes and between the conductor patterns can be reduced to about 0.3 mm at its minimum. Accordingly, high density mounting of the through holes and the conductor patterns can be realized.
The above through hole is a through hole extending through the insulating substrate, or a non-through hole not extending through the insulating substrate.
The above chemical plating film can be formed by the general chemical plating method.
Further, similar to the above case, the electric plating film can be formed on the surface of the conductor pattern by the general electric plating method.
The above laser beam can be constructed by using an excimer laser, a carbon dioxide gas laser, etc.
The process for forming the above conductor pattern and the plating lead may be performed before or after the boring process of the through hole. Otherwise, the process for forming the above conductor pattern and the plating lead may be also performed before or after the forming process of the above chemical plating film.
The printed wiring board of the fourth invention can be utilized in a multilayer printed wiring board requiring high connection reliability such as a memory module, a multichip module, a mother board, a daughter board, a plastic package, etc.